Right ventricular ejection has been attributed to a uniform reduction in the surface area of its free wall and to a reduction in the septal-to-free wall distance. This contraction pattern may lend itself to direct left ventricular assistance to right ventricular pump function. Even after total replacement of the right ventricular free wall with a Dacron patch or a Teflon cloth, the right ventricle still is able to develop pressure and outflow. This maintenance of right ventricular function may be due solely to septal contraction or conceivably, this maintenance of right ventricular function may represent a direct left ventricular assistance. This left ventricular assistance would occur directly not directly verified left ventricular assistance to right ventricular systolic function, nor have these studies determined the magnitude of this left ventricular assistance. Accordingly, this grant proposal will examine the following hypotheses: The left ventricle directly through the myocardium affects right ventricular systolic function; Under normal circumstances, at least half of right ventricular systolic function can be attributed to the left ventricle; Removing the pericardium will reduce left ventricular assistance; and, Regional ischemia will alter left ventricular assistance. The left ventricle can influence the right ventricle indirectly by altering output and directly through the myocardium. Accordingly, we will analyze transient changes in left and right ventricular pressures and dimensions following aortic and pulmonary vein constrictions to separate the direct (immediate) from the series (delayed) left ventricular effects on right ventricular pressures. Dimensional and pressure data will be recorded during aortic constriction (or release) and during pulmonary venous flow obstruction (or release). These measurements will be obtained with and without the pericardium. Additionally, these measurements will be obtained before and after creating ischemia restricted solely to the right ventricular free wall, the septum, or the left ventricular free wall. Computer analysis will separate the right ventricular systolic function. The analysis will also determine the magnitude of this left ventricular assistance. The new information obtained in this study will be of vital importance in understanding normal right ventricular function. Additionally, the information will help to explain the right ventricular response to ischemia and to pericardiotomy.